Field of the Invention
The invention resides in the telecommunications field. More specifically, the invention pertains to a digital telecommunication facility with one or more cordless mobile units.
Such a telecommunication facility is, for example, a radio system operating in accordance with the DECT standard.
The basic configuration of such a radio system is illustrated in FIG. 2:
The system of FIG. 2 includes a base station B and a plurality of cordless telecommunication terminals TE1 to TEn. In the exemplary embodiment, the cordless telecommunication terminals TE1 to TEn are mobile telephones which are capable of communicating with the base station B by radio.
Instead of the cordless telecommunication terminals TE1 to TEn or in addition to these, cordless connection sockets can be used for connecting wire-connected telecommunication terminals. The cordless telecommunication terminals, the cordless connection sockets, and similar facilities constitute the above-mentioned mobile units.
The data transmission between the base station B and the mobile units takes place in units of so-called frames or, more accurately, TDMA frames. The acronym TDMA stands for xe2x80x9cTime Division Multiple Accessxe2x80x9d and signifies that the frames are structured in such a manner that the base station can communicate consecutively in successive time slots (or slots) of a respective frame with all mobile units that are registered with it. The communication can then be effected by utilizing the full bandwidth of the transmission channel. The TDMA process is sufficiently well known and will, therefore, not be explained in further detail. The basic structure of a (TDMA) frame suitable for performing the TDMA process will now be explained with reference to FIG. 3.
The frame shown in FIG. 3, i.e. the DECT full-slot frame considered here, is composed of 24 time slots or slots (full slots) of identical length. The first 12 of the 24 slots are transmitted from the base station to the mobile units and the subsequent, second 12 slots are transmitted from the mobile units to the base station. More accurately, the zeroth slot of each frame is transmitted from the base station to a zeroth mobile unit, the first slot is transmitted from the base station to a first mobile unit, the second slot is transmitted from the base station to a second mobile unit, . . . , the eleventh slot is transmitted from the base station to an eleventh mobile unit. Conversely, the twelfth slot is transmitted from the zeroth mobile unit to the base station, the thirteenth slot from the first mobile unit to the base station, the fourteenth slot from the second mobile unit to the base station, . . . , and the twenty-third slot is transmitted from the eleventh mobile unit to the base station.
One frame, i.e. the 24 slots of a frame, is transmitted within 10 ms. Each slot comprises 480 bits and is transmitted within approximately 417 xcexcs (within 416.66 xcexcs). As indicated in FIG. 3, the 480 bits are distributed over a 32-bit-wide sync field, a 388-bit-wide D field, a 4-bit-wide Z field, and a 56-bit-wide guard space field.
320 bits are reserved within the D field for the transmission of the user data which are actually of interest (for example speech data). The base station can thus send user data comprising 320 bits to each of the mobile units and receive the same amount of user data from each of the mobile units within 10 ms; the transmission rate for user data between the base station and each of the mobile units is therefore 32 kbit/s in each direction.
The DECT standard thus enables high-quality systems to be implemented which can be used in a flexible manner. However, the DECT standard, but also other standards or pseudo standards, cannot always be used everywhere. It is especially because, as a rule, individual governmental regulations must be observed in the various transmitting frequency bands in which such radio systems are allowed to be operated, that, in most cases, completely new radio systems must be developed and implemented for utilizing newly released frequency bands.
This is associated with considerable technical effort, especially in the development of the required electronic components, because the integrated circuits used especially in this case cannot or in any case not easily be used in radio systems operating in a different manner.
It is accordingly an object of the invention to provide a telecommunications facility, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which can be obtained in a relatively simple manner from conventional telecommunication facilities even if it is principally designed for different technical requirements.
With the foregoing and other objects in view there is provided, in accordance with the invention, a digital telecommunication facility, comprising:
a base station and at least one cordless mobile unit;
the base station and the at least one cordless mobile unit being adapted to exchange data in units of two or more TDMA frames.
Provision of this feature creates the prerequisite for the capability of handling the data to be exchanged between the mobile units and the base station essentially as in conventional systems where communication takes place in units of individual frames. This is particularly true if, at the same time, the extent of the individual frames (i.e. the number of time slots or slots in the frame) is modified in such a manner that the total number of slots in the several frames treated as a unit is equal to the number of slots of a conventionally used (single) frame.
With an unchanged transmission period per frame, a changed number of slots per frame makes it possible to reduce the amount of data to be transmitted per unit time which is clearly reflected in a reduced bandwidth of the transmission channel.
In accordance with an added feature of the invention, the base station and the at least one mobile unit are TDMA units originally adapted to exchange data in units of individual, single TDMA frames and modified to exchange data in units of two or more TDMA frames.
In accordance with an additional feature of the invention, the base station and the at least one mobile unit are DECT units originally adapted to exchange data in DECT standard.
In accordance with another feature of the invention, a baseband chip for a telecommunication facility operating in the DECT standard is provided for the novel communication in the units of multiple TDMA frames.
In accordance with a further feature of the invention, the TDMA frames are divided into a number of slots, and wherein the units of two or more TDMA frames contain a constant number of slots independent of a number of TDMA frames in each unit.
In accordance with again an added feature of the invention, a structure and an extent of the slots is independent of a number of TDMA frames in each unit.
In accordance with again an additional feature of the invention, a time within which a TDMA frame is transmitted is independent of a number of TDMA frames in each unit.
In accordance with again another feature of the invention, a frequency divider divides a frequency of a bit clock determining a transmission speed of the telecommunication facility. In other words, the transmission of a frame remains the same independently of the number of slots comprised by it if, according to the invention, the (bit) clock with which the individual bits of a slot are sent out or received is changed.
In accordance with a concomitant feature of the invention, the base station and the at least one mobile unit, i.e. the novel telecommunication facility, are adapted to operate in a 2.4 GHz ISM band.
The handling of a number of frames, reduced in extent, as one coherent unit makes it possible in a particularly simple manner to change the bandwidth of the transmission channel and/or to adapt the telecommunication facility in other ways to the individual requirements. In particular, the complete AF part of the telecommunication facility can be taken over essentially unchanged from conventional telecommunication facilities.
As a result, a telecommunication facility operating or operated in this manner can be obtained in a relatively simple manner from conventional telecommunication facilities even though it was originally laid out for different technical specifications.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a digital telecommunication facility, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.